In order to meet a demand for wireless data traffic soring since a 4th generation (4G) communication system came to market, there are ongoing efforts to develop enhanced 5th generation (5G) communication systems or pre-5G communication systems. For the reasons, the 5G communication system or pre-5G communication system is called a beyond 4G network communication system or a post long term evolution (LTE) system.
For higher data rates, the 5G communication systems are considered to be implemented on ultra-high frequency bands (mmWave), such as, for example, 60 GHz. To mitigate pathloss on the ultra-high frequency band and increase the reach of radio waves, the following techniques are taken into account for the 5G communication system: beamforming, massive multi-input multi-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna, analog beamforming, and a large scale antenna.
Also being developed are various technologies for the 5G communication system to have an enhanced network, such as evolved or advanced small cell, a cloud radio access network (cloud RAN), an ultra-dense network, a device-to-device (D2D) communication, a wireless backhaul, a moving network, a cooperative communication, coordinated multi-point (CoMP), and an interference cancellation.
There are also other various schemes under development for the 5G system including, for example, hybrid frequency shift keying (FSK) and quadrature amplitude modulation (FQAM) and sliding window superposition coding (SWSC), which are advanced coding modulation (ACM) schemes, and filter bank multi-carrier (FBMC), non-orthogonal multiple access (NOMA) and sparse code multiple access (SCMA), which are advanced access schemes.
Communication systems are evolving to support a higher data rate to meet the demand for steadily increasing radio data traffic. For example, communication systems are in development to have enhanced spectral efficiency and increased channel capability based on a diversity of schemes including MIMO and the orthogonal frequency division multiplexing (OFDM) to increase the data rate.
As an example, the wireless local area network (WLAN) system adopts the multiple user-MIMO (MU-MIMO) scheme that enables sharing by multiple users and multiple antennas in order to support high-volume data services.
A soring number of stations (STAs) and users' demand for access to wireless networks led to an overlapped basic service sets (OBSS) environment, where multiple STAs and access points (APs) co-exist in one area. Under such an environment, the density of STAs and APs increases over time.
For instance, the number of STAs in a WLAN adopting the WLAN system is predicted to drastically grow as the D2D communication comes in commercial use.
Pursuant to the institute of electrical and electronics engineers (IEEE) 802.11-based medium access control (MAC) protocol which operates in a contention-based manner, simultaneous transmission of two or more signals at a particular time is deemed as a collision. For that reason, different APs and STAs using the same channel occupy and use the channel through mutual contention.
Under the OBSS environment, many STAs and APs use the same channel and are thus highly likely to collide. Further, such OBSS environment significantly worsens the hidden node problem that out-of-sensing coverage STAs attempt signal transmission without caring about each other and the exposed node problem that too many STAs are present in sensing coverage and are thus reluctant to make a transmission attempt. Accordingly, the overall network performance may be deteriorated.
In response, a research effort is underway via IEEE 802.11 to standardize schemes to mitigate inter-BSS interference while attaining an enhanced performance by varying the parameters of each BSS, such as, for example, sensing power, channel, transmit power, or beamforming direction, under the environment (i.e., OBSS environment) where different WLANs (BSSs) using the same channel overlap one another.
The architecture of a general WLAN system supportive of multiple antennas is now described with reference to FIG. 1.
FIG. 1 is a view schematically illustrating a structure of a general WLAN system supportive of multiple antennas according to the related art.
Referring to FIG. 1, a WLAN system includes multiple APs, for example, three APs including an AP#1 111, an AP#2, 121, and an AP#3 131, and multiple STAs, for example, nine STAs including an STA#1 113, an STA#2 115, an STA#3 117, an STA#4 123, an STA#5 125, an STA#6 127, an STA#7 133, an STA#8 133, an STA#8 135, and an STA#9 137.
The STA#1 113, the STA#2 115, and the STA#3 117 are connected with the AP#1 111 to form a BSS. The STA#4 123, the STA#5 125, and the STA#6 127 are connected with the AP#2 121 to form another BSS. The STA#7 133, the STA#8 135, and the STA#9 137 are connected with the AP#3 131 to form a BSS.
The STAs and the APs, if necessary, send signals when the number of slots where the channel is in an idle state is not less than a threshold number of slots. In the WLAN system, both uplink and downlink are implemented based on a contention-based scheme.
Accordingly, when a collision occurs on the uplink and downlink, the STAs and the APs perform a backoff operation in which they wait until the number of slots where the channel is in the idle state becomes more than the threshold number of slots and then send corresponding signals.
The structure of an environment where WLAN systems supportive of the normal contention scheme co-exist overlaid has been described above in connection with FIG. 1.
In other words, as set forth above, when multiple BSSs are present overlaid, a collision or performance deterioration is highly likely to occur, resulting in lowered STA transmission efficiency and overall network throughput, as well as a service delay.
Thus, a need exists for network management schemes for reducing performance deterioration and service delay in the WLAN system supportive of the OBSS environment.
The above-described data is provided only as background data for a better understanding of the present disclosure. No determinations and claims are made as to whether what has been described in this section may be applicable as the prior art related to the present disclosure.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.